柑桔测树学参数矫正法比较不同施肥水平对产量的影响

Tree dendrometric parameters modifying method to evaluate the effects of fertilization levels on citrus yields

【目的】柑桔树势对果实产量、品质均有很大的影响,以往局限于定性认识,野外试验也未做量化分析,树势差异对试验结果造成的影响难以准确评价。本项研究建立反映树势状况的测树学参数与单株产量的定量关系,进一步采用测树学参数矫正法比较施肥水平对单株产量的影响,为柑桔园合理施肥提供有效的分析方法和数据支撑。【方法】以柑桔为供试作物(品种为弗罗斯特脐橙),黄壤为供试土壤,进行了小区田间试验。试验共设7个施肥水平(f),以施肥量(N 112.50 kg/hm^2,P_2O_5 56.25 kg/hm^2和K_2O 75.00 kg/hm^2)的1.00、1.67、2.33、3.00、3.67和4.33倍设置6个处理,以不施肥为对照。观测了树高(H)、树冠直径(D)、主杆茎周(d)和单株产量(y)。采用测树学观测和回归分析,建立衡量树势状况的测树学参数与单株产量的线性方程,且用于滤除树势差异对产量形成的贡献,矫正树势差异对单株产量(y)的影响。在此基础上,分析不同施肥水平对矫正后单株产量(Y)影响规律,确定最高产量和所需施肥量。【结果】供试脐橙树冠体积与主杆茎周乘积的无量纲参数(DDdH)与单株产量呈极显著线性回归(y=38.35×DDdH+23.72)。矫正前后单株产量变化与施肥量变化之间均呈二次曲线回归,但矫正前回归方程F检验不显著。剔除树势差异对产量的贡献,在均一树势下,矫正后产量与施肥量之间的二次曲线回归的F检验和各项系数的t检验均达到显著水平。依据二次回归方程(Y=–2.44f^2+9.05f+41.09)计算,在氮磷钾施肥水平为N 208.1 kg/hm^2、P_2O_5 104.1 kg/hm^2和K_2O 138.8 kg/hm^2下,最高单产为31 t/hm^2。【结论】在品种、树龄和管理措施一致的前提下,脐橙树冠体积与主杆茎周乘积的无量纲参数与单株产量呈线性回归,利用回归方程可以有效矫正不可目测的树势差异对产量变化的贡献,从而准确分析施肥对单株产量的影响,用于指导脐橙园施肥。建立衡量树势状况的测树学参数与单株产量之间的定量关系,不仅对于果园管理具有重要的现实意义,对于柑桔及其他多年生果树的野外试验观测及数据处理具有借鉴价值。

[Objectives]Citrus tree vigor is an important determinant for fruit yield and quality, but previous studies are limited to qualitative analysis, and effects of the variance of tree vigor on field trials are not accurately disclosed. In this paper, a quantitative relationship between citrus yield per plant and dendrometric parameters was established to indicate the tree vigor, a dendrometric parameters adjusting method was explored to disclose the effects of fertilizer doses on citrus yields, and this method was used to determine the rational fertilizer rate for citrus sloping land.[Methods]A micro plot field experiment was conducted in terraced land （yellow soil） using a frost naval orange as material. Taking the fertilizer rates of N 112.50 kg/hm^2, P2O5 56.25 kg/hm^2 and K2O 75.00 kg/hm^2 as standard, six levels of 1.00, 1.67, 2.33, 3.00, 3.67 and 4.33 times of the standard were setup, with no fertilization as contrast. Citrus tree height （H）, crown diameter （D）, main stem perimeter （d） and single plant yield （y） were investigated. The linear regression of tree dendrometric parameters and yield per plant was established, which was used to correct contribution of plant vigor on variation of the yield per plant. The fertilization levels on single plant yield was more accurately analyzed, and the amount of fertilizer required for the highest yield per plant was calculated.[Results]The dimensionless parameter （DDdH） of dendrometric variables, citrus crown volume times the main stem weeks, showed a linear regression with the yield per plant （y=38.35×DDdH＋ 23.72）. At the average value of DDdH of all the tested plants, the modified yields of each plant （y） were calculated, and quadratic regressions between the yields per plant and fertilization levels （f） were acquired before and after the modification. Before the modification, the regression equation between y and f was not significant under the F test level, while after the modification, the quadratic curve regression between Y and f was significant at level of P 〈 0.01 （F test）, and the regression coefficients and constant items were all at significant levels （Y=-2.44f2 ＋ 9.05f ＋ 41.09） （t test）. According to the regression equation, at the average value of DDdH, the maximum yield was 49.46 kg per plant under the NPK fertilization levels of N 208.1 kg/hm^2, P2O5 104.1 kg/hm^2 and K2O 138.8 kg/hm^2.[Conclusions]Under the premise of consistent varieties, tree ages and management measures, the dimensionless parameter of fruiting citrus tree dendrometric variables, citrus crown volume times the main stem weeks, was linearly regressed with the yield per plant, and the regression could be used to disclose contribution of the variance of tree vigor to the variance of yield per plant and to accurately analyze the effects of fertilization levels on yields per plant, which would facilitate citrus orchard nutrient management. Setting up the quantitative relationship between the citrus tree vigor parameters and the yield per plant was important not only for the management of orchards, but also for the field observation and data processing of citrus and other perennial fruit trees.